ICDs: Implantable Cardioverter Defibrillators

Your heart is “wired” to beat in a specific way. The rhythm of the heart is very organized and controlled by a built-in electrical system. The SA node, the heart’s own natural pacemaker, signals it to relax and contract in a regular rhythm. Usually your heart rate is regular and beats between 60 and 100 times per minute. When you rest or sleep, it beats more slowly. When you are active, it beats more quickly. The SA node controls all of this. Located in the right atrium, the special “pacemaker” cells that make up the SA node send impulses to the AV node. The AV node is located in the center of the heart and acts as a relay between the atria and the ventricles. When the SA node “fires”, the atria contract and an impulse passes to the AV node. Once the impulse passes through the AV node, it travels through nerve fibers to the bottom of the ventricles. The ventricles contract and squeeze blood out of the heart. These actions produce a wave-like pumping pattern.